The present invention relates to a sunshine sensor and an air conditioner for a vehicle or car, and in particular, to a sunshine sensor and an air conditioner for a vehicle or car employing the sensor in which an intensity of the sunshine, an angle of elevation of the sunshine, and an angle of an azimuth of the sunshine can be sensed and which includes three light receiving elements to easily obtain the sunshine intensity as a total of outputs from these elements.
Conventionally, to cope with a remarkable change caused by a variation of a sunshine condition in the effective temperature of a user in a car, the air conditioner for the car senses states of the sunshine irradiated onto the car such as an amount of the illuminated light and an irradiation angle of sunshine so that depending on the amount of sunshine and the sunshine irradiation angle, an appropriate air blow-off exit thereof is selected to adjust a temperature of a blow-off air and a blow-off air flow rate, thereby achieving the sunshine correction control to appropriately regulate the distribution of the conditioned air in an interior room of the car. In this sunshine correction control, the operation of the air conditioner is not regulated only by the measured temperature in the car and the temperature preset by the user. Namely, there are additionally achieved control operations e.g. for an increased amount of the irradiated sunshine, the flow-off air temperature is lowered according to the amount; alternatively, an appropriate air blow-off exit of the air conditioner is selected depending on the sunshine illuminating direction to adjust the flow rate of the blow-off air.
In order to sense the sunshine states, this air conditioner employs a sunshine sensor. Sensors applicable to the conditioner have been described, for example, in the JP-A-1-136811, JP-A-1-136812, and JP-A-63-141816.
Each of the sunshine sensors respectively described in the JP-A-1-136811 and JP-A-1-136812 includes a pair of light receiving elements which are inclined with respect to a car moving or advancing direction and which are symmetrically inclined with respect to a horizontal direction vertical to the car moving direction. Using these light receiving elements, whether the sunshine is illuminated from the right or left is judged; moreover, the intensity thereof is also sensed.
In addition, according to the JP-A-63-141816, a pair of first sunshine sensors are disposed such that one of the sensors is arranged at a position in a car advancing direction (+X axis) and the other one thereof is installed at a position in a direction (-X axis) opposite thereto. More concretely, these light receiving elements are arranged along the X axis to be symmetric with respect to a direction (Y axis) vertical to the car advancing direction on a horizontal plane fixed to the car, the elements being inclined along a perpendicular direction (-Z axis). Moreover, a pair of second light receiving elements are respectively disposed at a position associated with a direction (+Y axis) toward the left with respect to the car advancing direction (+X axis) and at a position related to a direction toward the right (-Y axis) relative thereto. These light receiving elements are disposed along the Y-axis direction to be symmetric with respect to the X axis and to be inclined along the -Z axis direction.
In the sunshine sensor, the first light receiving elements are employed to detect an angle between the Z axis and a mapping result of the light beam onto the XZ plane, whereas the second light receiving elements are adopted to sense an angle between the Z axis and a mapping result of the light beam onto the YZ plane. Furthermore, the intensity of the sunshine is attained by computing the total of outputs from the four light receiving elements.
However, each of the sunshine sensors described in the JP-A-1-136811 and JP-A-1-136812 employing a pair of light receiving elements cannot detect a spatial azimuth of the light beam. Consequently, it has been impossible to correctly determine the azimuth and intensity of the illuminated light beam.
Moreover, in the sunshine sensor of the JP-A-63-141816, the light receiving surfaces of the respective light receiving elements are arranged about the Z axis to be rotationally symmetric with an angular discrepancy of 90.degree. therebetween. The sum of normal vectors of the respective light receiving surfaces is oriented toward the upper direction of the perpendicular axis (+Z axis). In consequence, the maximum value of the measured value of the sunshine sensor is developed when the sunshine direction matches the perpendicular direction.
However, actually, due to presence of a roof of a car, the quantity of heat received by the car is not maximized even when the sunshine direction is identical to the perpendicular direction. Consequently, in the sunshine sensor of the JP-A-63-141816, when the total of the outputs from the respective light receiving elements is employed to decide the measured value of the quantity of heat received by the car, the resultant data contains a considerably large error.
In addition, although there has been implied a sunshine sensor adopting three light receiving elements, any particular considerations have not been given to the arrangement of the light receiving elements. Consequently, a characteristic of the outputs from the receiving elements is not optimized.